A triumph for some and a day of sadness and recklessness for others - here's what people are saying about the triggering of Article 50.

:: Prime Minister Theresa May

"This is a historic moment from which there can be no turning back. Britain is leaving the European Union. We are going to make our own decisions and our own laws.

Video:PM on Brexit: 'There can be no turning back'

"We are going to take control of the things that matter most to us, and we are going to take this opportunity to build a stronger, fairer Britain. A country that our children and grandchildren are proud to call home."

:: Former UKIP leader Nigel Farage

Video:Farage toasts the triggering of Article 50

"Today's the day for me - after 25 years of campaigning - that the impossible dream came true. I'm delighted."

:: European Council President Donald Tusk

"There is no reason to pretend that this is a happy day, neither in Brussels nor in London. After all, most Europeans, including almost half the British voters, wish that we would stay together, not drift apart."

Video:Tusk: 'I will not pretend I am happy today'

"We already miss you. Thank you and goodbye."

:: German chancellor Angela Merkel

Image:Merkel: 'We did not wish for this day'

Germany and its partners "certainly did not wish for this day" but the EU will take a "fair and constructive" approach in Brexit talks.

"The negotiations must first clarify how we will disentangle our interlinked relationship... and only when this question is dealt with, can we, hopefully soon after, begin talking about our future relationship."

:: Scotland's First Minister Nicola Sturgeon

Image:First Minister Nicola Sturgeon

"Today, the PM will take the UK over a cliff with no idea of the landing place. Scotland didn't vote for it and our voice has been ignored."

:: EU chief Brexit negotiator Michel Barnier

"Today is the first day in a very long and difficult road. The EU will look to establish a fair agreement for the long term future of union members."

:: Labour leader Jeremy Corbyn

"The direction the Prime Minister is threatening to take this country in is both reckless and damaging.

Video:Corbyn responds to May's Article 50 letter

"Labour will not give this Government a free hand to use Brexit to attack rights, protections and cut services.

"It would be a national failure of historic proportions if the Prime Minister comes back from Brussels without having secured protection for jobs and living standards."

:: Foreign Secretary Boris Johnson

"I think it's a very great and historic day and I think that our European friends and partners have every reason to be positive about the suggestions we're making...

Image:Boris Johnson: 'A very great and an historic day'

"We have every reason to be very, very confident about the outcome."

:: Liberal Democrat leader Tim Farron

"The Prime Minister is twisting the will of the people, leaping into the abyss without any idea of where our country will end up."